Chapter 20. Asia: ecological zones

Figure 20-1. Asia: ecological zones

Figure 20-1 shows the distribution of ecological zones in Asia. Table 20-1 contains area statistics for the zones by subregion and Table 20-2 indicates the proportion of forest in each zone by subregion.

TROPICAL RAIN FOREST

This zone covers the southwestern coasts of India and Sri Lanka, Myanmar and the eastern Himalayan foothills, the coastal lowlands of Southeast Asia, the Philippines and most of the Malay Archipelago.

The western coasts of the Asian continent are very wet owing to monsoonal rains. Viet Nam and the Philippines deviate from this pattern and their eastern coasts are wet. Across the zone, annual rainfall is everywhere more than 1 000 mm and often more than 2 000 mm. There is no dry season in the equatorial regions. Everywhere else there is a short dry season, generally one to four months. Temperatures are always high.

In the wettest parts of this extensive zone the prevailing vegetation type is dense moist evergreen forest. A striking characteristic is the occurrence of Dipterocarpaceae only to the west of Wallace's Line.[35] The mangrove forests of the Ganges Delta and western New Guinea are the most extensive in the world. In the drier parts of the area, mainly in eastern Indonesia and the Himalayan foothills, semi-deciduous or moist deciduous forests occur. In the Brahmaputra valley, these are valuable sal forests (Shorea robusta).

The lushest rain forests are found in the Malay Archipelago, harbouring a very rich flora. Over half (220) of the world's flowering plant families are represented as well as about one-quarter of the genera (2 400), of which about 40 percent are endemic. Of 25 000 to 30 000 species about one-third are trees of more than 10 cm in diameter. Dipterocarpaceae, which are particularly diverse in genera and species, dominate rain forests west of the Wallace Line. They contribute many (Sumatra, Malaysia), most (Borneo) or all (Philippines) of the top canopy giant trees. The main genera are Dipterocarpus, Shorea, Dryobalanops and Hopea. Other important tree families include Anacardiaceae, Ebenaceae, Leguminosae, Sapindaceae, Euphorbiaceae and Dilleniaceae. Pometia, Canarium, Cryptocarya, Terminalia, Syzygium, Casuarina and Araucaria are among the chief tree genera of forests east of the Wallace Line.

Table 20-1. Asia: extent of ecological zones

Subregion	Total area of ecological zone (million ha)
	Tropical						Subtropical					Temperate					Boreal			Polar
	Rain forest	Moist	Dry	Shrub	Desert	Mountain	Humid	Dry	Steppe	Desert	Mountain	Oceanic	Continental	Steppe	Desert	Mountain	Coniferous	Tundra	Mountain
Central Asia											1		1	135	308	99			1
East Asia		4				8	200				140		120	65	156	307	16
South Asia	31	58	98	119	57	12			22	5	41					5
Southeast Asia	272	79	49	2		46	1				1
West Asia					223	22	6	13	95	145	168		9	9	5	7
Total Asia	303	141	146	121	280	88	208	13	116	150	351		130	210	468	418	16		1
TOTAL WORLD	1 468	1 117	755	839	1 192	459	471	156	491	674	490	182	726	593	552	729	865	407	632	564

Note: Data derived from an overlay of FRA 2000 global maps of forest cover and ecological zones.

Table 20-2. Asia: proportion of forest by ecological zone

Subregion	Forest area as proportion of ecological zone area (percentage)
	Tropical						Subtropical					Temperate					Boreal			Polar
	Rain forest	Moist	Dry	Shrub	Desert	Mountain	Humid	Dry	Steppe	Desert	Mountain	Oceanic	Continental	Steppe	Desert	Mountain	Coniferous	Tundra	Mountain
Central Asia														3		6			72
East Asia		28				58	36				28		32	10		8	85
South Asia	53	23	58	8		79			7		22
Southeast Asia	55	46	79	*		56
West Asia							49	34			5		19			26
Total Asia	55	36	65	10		46	36	34	2		16		31	5	0	8	85		76
TOTAL WORLD	69	31	64	7	0	26	31	45	9	2	20	25	34	4	1	26	66	26	50	2

* Estimate uncertain because of discrepances in global forest cover map.
Note: Data derived from an overlay of FRA 2000 global maps of forest cover and ecological zones.

TROPICAL MOIST DECIDUOUS FOREST

This zone includes the lowlands of Sri Lanka; much of peninsular India; the hilly basin forming most of the country of Myanmar; the Red River valley and the lower foothills of the surrounding mountains in northern Viet Nam; the low plateaus on the western side of the Annamitic Range in southern Viet Nam, the Lao People's Democratic Republic and Cambodia; the plains and western foothills of the mountains in the Philippines; the low, flat, often swampy plains of the southern part of New Guinea and parts of Hainan Island and the Lezhou Peninsula in China.

Where the influence of the southwest monsoon is less, rainfall is generally between 1 000 and 2 000 mm with a dry season of three to six months. Temperatures are always high, with a mean temperature of the coldest month generally above 20°C but sometimes slightly lower, as in northern India, Myanmar or the Indochinese peninsula. In China, the southern parts of Lezhou and Hainan Island have a similar climate.

The natural vegetation is mostly deciduous or semi-deciduous forest, commonly known as monsoon forest. Many dominant trees belong to the Leguminosae, Combretaceae, Meliaceae or Verbenaceae. Dipterocarpaceae are also present, but less conspicuous than in the rain forest. Teak forests (Tectona grandis) in western and northern Thailand, the Lao People's Democratic Republic, Myanmar and peninsular India and sal forests (Shorea robusta) in eastern India and the Ganges valley are of great economic value. Tree species associated with the teak forest include Lagerstroemia spp., Xylia kerrii, Adina cordifolia, Vitex spp., Tetrameles nudiflora, Afzelia xylocarpa, Diospyros spp., Sindora cochinchinensis and Pinus merkusii. In the sal forests, tree species of Dillenia, Terminalia, Adina and Pterospermum are codominant. Bamboo brakes (Dendrocalamus strictus) are common in India and Myanmar. Extensive deciduous forests remain on hilly parts of Myanmar and some patches in northern Viet Nam on the Red River plain. In the remaining part of Indochina the zone is widely covered with deciduous dipterocarp and teak forest. In Papua New Guinea there is a different type of dry evergreen or semi-evergreen deciduous forest, characterized by species such as Garuga floribunda, Protium macgregorii, Intsia bijuga and Acacia spp. (Mimosaceae) and the presence of Myrtaceae, Proteaceae and Rutaceae.

In China, tropical moist deciduous forest is found below 700 m in basins and river valleys of the southern mountains on Hainan Island. The main species include Heritiera parvifolia, Amesiodendron chinense, Litchi chinensis, Vatica hainanensis, Diospyros hainanensis, Hopea hainanensis, Lithocarpus fenzelianus, Homalium hainanensis, Podocarpus imbricata. The middle layer of the rain forest often includes Dysoxylum binectariferum, Sindora glabra, Ormosia balansae, Pterospermum heterophyllum, Gironniera subaequalis, Schefflera octophylla, Dillenia turbinata and Hydnocarpus hainanense. Hill moist forest grows from 700 to 1 200 m and is composed of Altingia obovata, Manglietia hainanensis, Michelia balansae, Madhuca hainanensis and species of Fagaceae, Lauraceae, Theaceae, and Aquifoliaceae. In the central part of the island, coniferous forests grow on low mountains and hills at altitudes below 800 m. Pinus latteri dominates and forms second-growth pure forests or mixtures with Liquidambar formosana, Chukrasia tabularis and Engelhardtia roxburghiana. Mangrove forests grow along shorelines around the island except for the west coast. Tree species include Avicennia marina, Rhizophora mucronata, R. apiculata, Bruguiera conjugata, B. cylindrica, Ceriops tagal, Sonneratia acida, Xylocarpus granatum and others.

TROPICAL DRY FOREST

The zone comprises the coastal plains along the Gulf of Bengal and the northeastern part of the Deccan Plateau in India and Sri Lanka. In Myanmar, it includes the basin around Mandalay. The zone occupies the wide, flat alluvial basin of the Chao Phraya River in Thailand as well as the Korat Plateau and the Mekong River valley. In Cambodia, the area is the whole low central plain built by the lower Mekong River and the Tonle Sap. The Mekong delta in Viet Nam is part of this zone. Narrow coastal stretches also occur in southern Papua New Guinea.

These areas are sheltered from the humid winds blowing from the oceans and only partially receive, in summer, the southwest monsoon. In winter they are influenced by the dry winds of the northeast monsoon. Rainfall ranges between 1 000 and 1 500 mm, with a dry season of five to eight months. Mean temperature of the coldest month is always above 15°C, often 20°C.

Dry evergreen forest occurs on the dry eastern Coromandel Coast of India and in northern Sri Lanka. The vegetation is a stunted woody formation with Manilkara hexandra, Chloroxylon swietenia, Albizia amara and Capparis zeylanica.

Dry deciduous dipterocarp forests and woodlands are more common throughout Viet Nam, the Lao People's Democratic Republic, Cambodia and Thailand. Characteristic species include Dipterocarpus intricatus, D. obtusifolius, D. tuberculatus, Pentacme siamensis and Shorea obtusa. In Thailand, some of these woodlands include teak (Tectona grandis) and a pine species (Pinus merkusii).

In mixed deciduous woodlands, teak and pine occur with dipterocarps or Leguminoseae. They are found in Thailand, Myanmar, the Lao People's Democratic Republic and Viet Nam. In India, woodlands are also common but only a few dipterocarps occur, notably Shorea robusta and S. talura. In southern Papua New Guinea there are some dry deciduous forests with Myrtaceae and Eucalyptus woodland.

TROPICAL MOUNTAIN SYSTEMS

Tropical mountain systems include the eastern Himalayas; mountains stretching from Tibet to northern Indochina, the Malaysian Peninsula and the Annamitic Range; the central mountain ranges of the islands of Indonesia and the Philippines; relatively high peaks (over 2 000 m) in India and Sri Lanka; and mountains in the southwestern Arabian Peninsula.

Most tropical mountains of Asia, i.e. those reaching at least 1 500 to 2 000 m, have a wet climate. The Himalayas have a subtropical northwestern part and a tropical wet southeastern part. Nepal is a transitional region between these two areas. In all tropical mountains, between 1 000 to 1 500 m and 4 000 m, annual precipitation is more than 1 000 mm, sometimes more than 2 000 mm. There is a pronounced dry season of three to five months in the submontane zone of the eastern Himalayas, with the mean temperature of the coldest month above 15°C. Everywhere else, the dry season, if it occurs, is very short. The mean temperature of the coldest month rapidly decreases with increasing elevation. Above 4 500 to 5 000 m there is permanent snow.

The mountains in the southwestern Arabian Peninsula have a drier climate. Annual rainfall ranges from 400 mm in the lower foothills to 800 mm on the higher escarpments. There are two rainy seasons, March to April and July to September.

Forests generally cover the Himalayan slopes up to 4 000 m. Beginning around 1 000 m, tropical lowland forest is replaced by an evergreen forest with Castanopsis, Schima, Engelhardtia and Lithocarpus species and, locally, Himalayan chir pine forest (Pinus roxburghii). From 2 000 to 3 000 m is a belt of evergreen oak forest, followed higher up by coniferous forest (Abies spp., Tsuga spp.).

In Myanmar and Thailand, evergreen oak forests are found above 1 500 m with pine forest. An evergreen forest with Lauraceae and Fagaceae grows from 1 500 to 2 000 m in the Lao People's Democratic Republic and Viet Nam while a mixed broad-leaved/coniferous forest takes over above this elevation. Woodlands with oaks and pines also occur at high altitude. In Thailand, northern Lao People's Democratic Republic and Viet Nam, these forests have been affected by shifting cultivation and mosaics of forests and thickets predominate at lower elevations.

In Malaysia, as well as in Indonesia and the Philippines, the montane (evergreen) rain forest still covers relatively large areas. This forest is best developed between 1 400 and 2 400 m altitude and is characterized by Fagaceae (of the genera Castanopsis, Lithocarpus and Nothofagus in Papua New Guinea), Lauraceae, Juglandaceae (Engelhardtia spp.), Magnoliaceae (Casuarina junghuhniana), conifers (Podocarpus spp. and Pinus spp. in Sumatra), Dacrydium spp., Araucaria spp., Libocedrus spp., Phyllocladus spp. and others. In the subalpine zone, between 2 400 and 4 000 m, dense or discontinuous montane thickets are found. Coniferous forest containing Araucaria spp., Podocarpus spp. and/or Libocedrus spp. often occurs in this belt. The alpine zone extends above 4 000 m.

Mountains are the only locations on the Arabian Peninsula where forests grow. From around 1 000 to 1 500-1 800 m is Acacia-Commiphora deciduous scrub or savannah. From 1 500-1 800 to 2 000 m is evergreen woodland or forest with Olea africana, Podocarpus spp., Olea chrysophylla, Trochonanhus comphoratus and other species while from 2 000 to 3 000 m is coniferous forest of Juniperus procera.

SUBTROPICAL HUMID FOREST

This ecological zone has its main distribution in southeastern China south of the Yangtze River, the southern tip of the Republic of Korea and the southern half of Japan. There are two distinct small geographic units in the Near East, humid forests at the foot of the Caucasus Mountains extending westward along the Black Sea and in the foothills of the Talysh Mountains at the Caspian Sea.

Winters are mild to warm and summers are hot and wet. Northerly cold fronts from Siberia heavily influence winter temperatures while in summer the Pacific monsoon brings large amounts of precipitation to the region.

Annual mean temperatures in China and the Korean Peninsula range from 15° to 17°C in the northern part of the zone to around 21°C in the south and southeast. Annual precipitation varies between 800 and 1 300 mm throughout the northern region, but further south it becomes wetter, up to 1 800 mm and sometimes 2 500 mm in low mountains. Annual rainfall diminishes towards the west, away from the coast. In the northern and central parts of the zone rainfall is evenly distributed throughout the year. In the south, most of the rain falls between May and October. A dry season from November to April is distinctive. The island of Taiwan Province of China is under the strong influence of the maritime monsoon climate, with higher average temperatures and greater rainfall.

The climate in Japan is greatly influenced by the monsoon. Generally speaking, the summers are very hot and the winters rather cold with snow and frosts. Mean annual temperature is around 14° to 17°C. The yearly precipitation over most of Japan is much greater than over the continent. Mean annual precipitation ranges from around 1 200 mm to more than 2 500 mm locally with two peak rainy seasons, "Baiu" (June to July) and "Shurin" (autumn rain).

The climate of the coastal plains and lowlands south of the Black Sea and the Caspian Sea is warm-temperate with an annual average temperature around 14° to 15°C. Large amounts of precipitation fall throughout the year (1 500 to 2 000 mm, locally up to 4 000 mm). In the Colchis area the climate is mild owing to the influence of the Black Sea (yearly amplitude of the monthly average temperatures 15° to 19°C), with mild winters (average temperature of the coldest month 5° to 6°C).

Two types of woody vegetation prevail south of the Yangtze River in eastern China, pine forest and deciduous forest mixed with evergreen species. The dominant conifer here is Pinus massoniana. The mixed deciduous evergreen forests, a unique subtropical vegetation type, include Quercus acutissima, Q. variabilis, Q. dentata, Q. glandulifera, Q. fabrei, Liquidambar formosana, Pistacia chinensis, Ulmus parvifolia, Zelkova schneideriana, Celtis sinensis, Dalbergia hupeana, Albizia macrophylla, Tilia miqueliana, Cyclobalanopsis glauca, C. myrsinaefolia, Castanopsis sclerophylla, C. carlesii, Lithocarpus glabra, Phoebe sheareri, Cinnamomum chekiangense, Machilus thunbergii and Ilex purpurea. Bamboo stands are common in the region, with more than 20 species of Phyllostachys of which P. edulis is most common.

The western mid-latitude mountains feature conifer forests dominated by such species as Abies chensiensis, A. fargesii, A. ernestii, Picea complanata and P. neoveitchii as well as Pinus armandii, P. henryi and Platycladus orientalis. Pinus tabulaeformis and P. bungeana forests are distributed over western portions of the Qinling Range. Deciduous broad-leaved forests contain more than 300 woody species, the major trees including Quercus acutissima, Q. variabilis, Q. liaotungensis, Q. aliena var. acuteserrata, Q. dentata, Q. glandulifera, Betula albo-sinensis and Toxicodendron vernicifluum.

In the southeastern low mountain and hill region as well as the Sichuan Basin the representative vegetation is typically evergreen broad-leaved forests as well as coniferous forests. Distributed across the entire region is an evergreen broad-leaved laurel forest of Cyclobalanopsis glauca. There are Castanopsis eyrei and C. fargesii in the central to northern parts of the area and C. hystrix and C. lamontii from the western to eastern sides of the Nanling Mountains. Conifer forests are primarily those of Pinus massoniana, P. taiwanensis and Cunninghamia lanceolata. The region is one of the most important bamboo regions in China. There are two million hectares of Phyllostachys edulis in the area. Several other species from the same genus, P. bambusoides, P. nidularis, P. mannii, P. nigra var. henonis and P. heteroclada, also occupy a broad range.

On the Yungui Plateau in southern and southwestern China, regional evergreen broad-leaved laurel forests are similar to those of eastern areas, consisting the same genera, Castanopsis, Lithocarpus, Cyclobalanopsis, Cinnamomum and Phoebe, but often with different species. The conifer forest here is dominated by Pinus yunnanensis, which grows widely from 1 000 to 3 100 m, with pure stands usually from 1 600 to 2 800 m.

The forests of Taiwan Province of China are distributed along a distinct gradient from the coastal region to the high mountains. Mangrove forests occur along shallow shorelines. Southern subtropical rain forest covers low hills (below 500 m) in northern Taiwan. Major upper-storey species include Cyclobalanopsis glauca, Castanopsis carlesii, C. kusanoi, Ficus microcarpa, Cryptocarya chinensis, Acer oblongum, Elaeocarpus japonica, Ilex rotunda and Engelhardtia roxburghiana. Evergreen broad-leaved forests extend to 500 to 1 800 m slopes and include Castanopsis kawakamii, C. fargesii, C. uraiana, Lithocarpus brevicaudatus, L. ternaticupula, L. amygdalifolius and Cinnamomum camphora.

The predominant natural vegetation in Japan is evergreen broad-leaved forest of several types. The major tree species are Machilus thunbergii and Castanopsis cuspidata in coastal areas and Cyclobalanopsis glauca, C. gilva. C. salicina, C. myrsnaefolia and C. acuta (evergreen oaks) in inland areas. Conifers, such as Podocarpus macrophyllus, P. nagi and Torreya nucifera also occur in these forests. At higher elevations, Tsuga sieboldii and Abies firma grow in mixture with the broad-leaved evergreen species. The medium to lower strata contain small trees and shrubs of such broad-leaved evergreen species as Aucuba japonica, Damnacanthus indicus and Neolitsea sericea. Secondary forests of Pinus densiflora, Quercus serrata and Quercus acutissima now cover large areas. Natural stands of Pinus densiflora are restricted to extreme habitats.

The two forests in the Near East, although of relatively small extent, are the most diverse and productive in the region. Both forests are dense broad-leaved summer-green types. The forest canopy consists of oak species (in the west Quercus imeretina, Q. hartwissiana, in the east Q. castaneifolia) and also Castanea sativa, Pterocarya pterocarpa, Diospyros lotus and Fagus sylvatica subsp. orientalis. Zelkova carpinifolia, Carpinus betulus and some Acer species are present in the subcanopy layer. At higher altitudes mixed hornbeam-oak forests (Quercus iberica, Carpinus orientalis, Fagus sylvatica subsp. orientalis and Castanea sativa) replace this vegetation. Small areas of swamp and fen forests (Alnus barbata, A. subcordata, Pterocarya pterocarpa) occur along riverbanks and estuaries.

SUBTROPICAL DRY FOREST

This zone is confined to the Near East and occupies a relatively narrow belt along the Mediterranean Sea and the low hills running parallel to the coast. The northern part of the Jordan-Arava Rift Valley is also included.The zone has a typical Mediterranean climate with mild, humid winters and dry, moderately hot summers. Annual rainfall ranges from around 400 to 800 mm, decreasing from north to south.

Various types of pine forest occur, with either Aleppo pine (Pinus halepensis), P. brutia or P. pinea as dominant species. Otherwise, the typical Mediterranean woody maquis vegetation dominates this zone. Ceratonia-Pistacia lentiscus maquis dominates the coastal plains up to around 200 m, while Quercus calliprinos-Pistacia palaestina maquis is the main vegetation from 200 to 1 000-1 200 m. Other important tree species include Quercus ithaburensis, Q. infectoria, Q. ithaburensis, Q. coccifera, Laurus nobilis, Arbutus andrachne, Cercis siliquastrum, Juniperus phoenicea, Myrtus communis, Olea europaea, Phillyrea spp., Pinus halepensis and P. brutia.

SUBTROPICAL STEPPE

This zone is confined to western Asia, mainly the Near East but also in Afghanistan and Pakistan. The climate is semi-arid. Annual rainfall ranges from about 200 to 500 mm and falls during winter in the Near East. Eastern Afghanistan and Pakistan receive most of their rainfall from June to September. Although differences in temperature between seasons are relatively high, winters are not severe.

The vegetation consists of low shrubs and grasses interspersed with sparse trees, particularly at wetter locations. At higher, more humid locations in the Near East a forest-steppe can be found with trees such as Amygdalus korshinskyi, A. arabica, Acer monspessulanum, Pistacia atlantica, Pyrus bovei, Rhamnus palaestina and Crataegus aronia. In Pakistan, the woody steppe vegetation consists of shrubs and small trees. Main species are Acacia modesta and Olea cuspidata accompanied by Ziziphus jujuba, Dodonea viscosa and others. Owing to prolonged human activity the original vegetation has been considerably altered.

SUBTROPICAL MOUNTAIN SYSTEMS

Subtropical mountain systems cover extensive areas in Asia in a nearly continuous west-east belt from the mountains and highlands of Turkey to the eastern reaches of the Himalayas in southern China.

The climate of the Near Eastern mountain systems is extremely diverse, both in temperature and rainfall. Winter precipitation is predominant, ranging from 500 to 1 400 mm. The rainy season is from around September to May or June, while the rest of the summer is dry and hot.

All along the Himalayan ranges the rainfall increases from west to east and the climatic regime changes gradually from Mediterranean to typical monsoon types. The rain also decreases from the outer to the inner parts of the ranges. At the submontane and montane levels, rainfall ranges from less than 1 000 to 1 500 mm, with at least one or two dry months even up to seven or eight. The mean temperature of the coldest month varies from around 15°C in the submontane zone to less than 10°C above 2 000 m. Snow occurs above 3 000 m, with frequent winter frost. Precipitation is 500 to 1 000 mm.

China's subtropical mountains comprise the central interior highlands and southwestern high mountains. The region has a harsh climate at high elevations but warmer, moist conditions in the medium to low mountains. Annual mean temperature ranges from 8° to 18°C in eastern areas with the January mean above 0°C and the extreme low at -20°C. Annual rainfall is 800 to 1 200 mm, up to 3 000 mm locally. A dryer and colder climate prevails towards the western higher mountain areas. In southern Tibet, mean annual temperatures in the mountains are 6° to 8°C, average in winter is 2° to 4°C and in summer around 15°C. Annual precipitation ranges from 300 to 700 mm. River basins in the south at 500 m elevation are relatively warm and moist with annual rainfall more than 1 200 mm and a distinct dry-rainy seasonal change as a result of the impact from the Indian Ocean monsoon.

Mediterranean mountain vegetation is diverse and includes dense humid forests, shrubland, forest-steppe and treeless grass steppe. The forests can be either deciduous broad-leaved or coniferous. In Lebanon and the Syrian Arab Republic a summer-green oak forest is found between 1 000 and 1 600 m altitude. The forest climax is Quercus cerris accompanied by Quercus boissieri and fragments of Quercus libani. In western Turkey, black pine (Pinus nigra) dominates this belt. From 1 500 to 2 000-2 200 m, there is a subalpine coniferous forest with cedar (Cedrus libani), fir (Abies cilicica) and juniper (Juniperus excelsa). Juniper forest occupies the drier areas. Above 2 200 m, alpine dwarf shrubs and meadows occur.

Forest-steppe and steppe vegetation occupy major parts of the central highlands and plateaus of Turkey and Iran. At humid locations grows a deciduous oak forest dominated by Quercus persica or other oak species, often in combination with juniper (Juniperus spp.). In the valleys there are Fraxinus oxycarpa, Platanus orientalis and Ulmus campestris as well as various species of Populus, Salix, Tamarix, etc. Tree steppe with pistachio, almond and juniper occur at sub-dry locations.

Well-developed forest grows on the higher slopes of the mountains bordering the Black and Caspian Seas. At both locations we find summer-green dense forest between approximately 800 and 2 000 m. The Hyrcanian montane forest is Fagetea hyrcanica with Fagus orientalis, accompanied by Carpinus betulus, Acer insigne and Quercus castaneifolia. The Euxinian montane forest is composed of deciduous broad-leaved trees and conifers with species of oak, fir and pine.

Vegetation of the northwestern and western Himalayas is extremely diverse. In southern Afghanistan, open deciduous woodland is the dominant vegetation at medium high altitudes. Pistacia atlantica woodland 4 to 6 m high occurs from around 1 100 to 1 800-2 000 m. Between 2 000 and 2 800 m, Amygdalus communities prevail (Amygdalus cf. communis, A. kuramica and Fraxinus xanthoxyloides).

In eastern Afghanistan and Pakistan, different types of west Himalayan evergreen sclerophyllous forests and woodlands occur. Woodland of Quercus baloot is most extensive and occurs at an altitude of around 1 300 to 2 000 m. Depending on the water supply, they are either open woodlands with stunted trees 3 to 6 m high or true forests with trees 15 m or more in height. Quercus dilatata and Quercus semecarpifolia communities are confined to the higher parts of wet mountains. The first dominates between 1 900 and 2 400 m, the latter from 2 400 to 2 900 m. Both species form rich, mesophylous forests 8 to 20 m in height.

Coniferous forests are the most extensive mountain forests. Chir pine (Pinus roxburghii) forests dominate the lower mountain slopes from 900 m up to 1 700 to 2 000 m altitude, accompanied by some oaks (Quercus dilatata) and other broad-leaved species. West of the Indus, Pinus gerardiana forest is found between 2 000 and 2 500 m. A dense forest of Cedrus deodara is found between 2 500 and 3 100 m in areas with 450 to 650 mm annual rainfall. Other trees of this forest are Picea morinda, Pinus excelsa and Abies webbiana. With decreasing rainfall, Juniperus seravschanica gradually replaces the cedar. East of the Indus, increased precipitation favours blue pine (Pinus wallichiana). A dense, mixed forest dominated by Picea smithiana and Abies webbiana grows in high rainfall areas (greater than 800 mm per year) between 2 900 and 3 200 m. In areas with winter rains, Juniperus spp. woodlands dominate at altitudes ranging from 1 500 to 3 000 m. Further eastward, under the monsoon-influenced climate, Juniperus woodland occurs above 3 000 m. Typical subalpine woody vegetation, ranging between 3 000 and 4 000 m altitude, is a mixture of conifers and broad-leaved low trees or shrubs. Main species are Abies webbiana, Abies spectabilis, Betula utilis and Rhododendron campanulatum.

In Azad Jammu and Kashmir, from 1 500 to 3 000 m, coniferous forests occur with Pinus excelsa and Cedrus deodara, mixed with thickets and grasslands. Above 3 000 m they give way to mixed forests and woodlands with Betula and Abies. To the east, from Himachal Pradesh to central Nepal, the submontane level from 1 000 to 2 000 m is characterized by open woodlands with Pinus roxburghii. Above 2 000 m, dense evergreen forests occur, with oaks or conifers (Cedrus deodara, Picea spp., Pinus excelsa), then Abies-Quercus forests above 3 000 m.

The alpine conifer forests of China are dominated by Abies faberi and Picea complanata, usually from 2 000 to 3 000 m. The species are often associated with Tsuga chinensis, Picea complanata, Acer spp., Tilia spp. and Betula albo-sinensis but form pure stands at higher altitudes, up to 4 000 m. Conifer forests that grow in pure stands on low and medium altitude mountains are Pinus massoniana, P. yunnanensis, Cunninghamia lanceolata and Cupressus funebris. Further west and at higher elevations are alpine conifer forests of highly cold-tolerant species dominated by Picea balfouriana and Abies squamata, which often form pure stands on north-facing slopes from 3 000 to 4 000 m.

Abies spectabilis and Picea linzhiensis are the dominant species in the alpine conifer forests of southern Tibet. The former species, also called Himalayan fir, is found in pure stands or in association with Abies georgei and Picea likiangensis in the southern part at 3 100 to 4 000 m on north-facing slopes. Picea linzhiensis forms pure stands in the southeast from 2 900 to 3 900 m. Conifer forests at medium elevations are dominated by Pinus griffithii. Southern subtropical monsoon rain forest occurs on valley lands under 500 m and is composed of Shorea robusta, Terminalia catappa, Tetrameles nudiflora and Dillenia pentagyna.

In central Taiwan Province of China, coniferous and broad-leaved mixed forests occupy mountain slopes from 1 800 m up to 3 000 m altitude. Major species include Chamaecyparis obtusa var. formosana and C. formosensis. Broad-leaved components include Cyclobalanopsis stenophylloides, Trochodendron aralioides, Acer formosum and Sassafras randaiense as well as lower-layer species from the genera Eurya, Ilex, Symplocos and Hydrangea. Alpine conifer forests occur in the Yushan and Bishan Mountains at elevations generally above 3 000 m with Abies kawakamii as the major species.

TEMPERATE CONTINENTAL FOREST

This zone includes the temperate forests of China, the Korean Peninsula and Japan. In China, the annual mean temperature varies greatly, from 2°C in the north to 14°C in the south. Climate is distinctly seasonal; winter is relatively long (four to seven months) and spring short (one to three months). In the northern part, warm summers have monthly average temperatures above 20°C in the warmest month and a growing season lasting 100 to 150 days. Annual precipitation is between 400 and 800 mm for most of the area to 1 000 mm over the southeastern part of the zone. In the southern part, mean temperature in the coldest months still falls below 0°C. Warm summers bring the average temperature up to 24°C in the warmest month except in the mountains. The growing season lasts 200 days. Annual precipitation of 600 to 1 000 mm is unevenly distributed over the year. Coastal areas experience higher rainfall, 1 000 to 1 400 mm. Similar climatic conditions prevail on the Korean Peninsula and in northern Japan.

The northern part of the zone (in northeastern China) features well-stocked Pinus koraiensis mixed forests on low mountains of 400 to 600 m. Associated species include Picea jezoensis var. microsperma, Picea koraiensis, Abies nephrolepis, Betula platyphylla, B. costata, B. davurica, Populus davidiana, Quercus mongolica, Tilia amurensis, Acer mono, A. ukurunduense, A. tegmentosum, Ulmus davidiana var. japonica, Fraxinus mandshurica and Juglans mandshurica. Once disturbed, the mixed forests usually degrade into Populus davidiana and Betula platyphylla second-growth forests. Pinus koraiensis mixed forest in Changbaishan has a similar composition but more species, adding Abies holophylla, Pinus sylvestris var. sylvestriformis, P. densiflora, Taxus cuspidata, Thuja koraiensis, Fraxinus rhynchophylla and several maple and linden species.

In contrast to the generally forested eastern part of northeastern China, the rest of the zone has little tree cover left. Pockets of natural second-growth forests exist, represented by Pinus densiflora, P. tabulaeformis and several deciduous oaks, including Quercus acutissima, Q. variabilis, Q. dentata, Q. aliena, Q. serrata, Q. liaotungensis and Q. mongolica. Planted species in the countryside are mostly Populus, Salix and Ulmus species and Sophora japonica, Ginkgo biloba, Platycladus orientalis, Sabina chinensis, Paulownia fortunei, Catalpa bungei, Castanea mollissima, Diospyros kaki, Ziziphus jujuba, Toona sinensis, Ailanthus altissima and Robinia pseudoacacia. Cultivated bamboo stands are scattered in the plains, mostly Phyllostachys glauca, P. vivax, P. bambusoides and P. propinqua. The region also has reported some successful agroforestry experiments using fast-growing timber species, Populus and Paulownia for instance.

The temperate forests of Japan are deciduous, summer-green, broad-leaved forests dominated by beech. The main trees are Fagus crenata, Kalopanax septemlobus, Tilia japonica, Quercus mongolica var. grosseserrata, Acer mono, etc. Moist habitats in valley bottoms and on alluvial fans support Pterocarya rhoifolia forests with Ulmus laciniata, Athyrium pycnocarpon, Acer mono, Dryopteris crassirhizoma and others. Habitats with a high water table in the lowlands of northern Honshu and Hokkaido support Alnus japonica forest.

TEMPERATE STEPPE

This ecological zone encompasses the vast steppes of Central Asia, occupying the eastern part of Inner Mongolia in China and central and eastern Mongolia.

The zone has a long, cold winter and a short, but warm, summer. Annual average temperatures vary between 2° and 10°C, with mean temperatures of the coldest month (January) ranging from -10° to -20°C. Mean temperature reaches 24°C in the warmest summer month. The growing season lasts 100 to 175 days. Annual rainfall ranges from 200 to 400 mm, locally up to 600 mm, and the maximum occurs during the second half of summer. Spring, as a rule, is dry.

Natural vegetation is primarily grass and shrub steppe. In some areas, pockets of woodland can be found. Tree species are represented by Pinus tabulaeformis, P. bungeana, Picea wilsonii, P. meyeri and Larix principis-rupprechtii, individually forming pure stands or sometimes admixed with Abies nephrolepis. Populus davidiana and Betula platyphylla come in from the northeast to form second-growth pure or mixed stands when spruce forests are disturbed while Populus cathayana is common in valleys and lowlands.

TEMPERATE MOUNTAIN SYSTEMS

The vast mountain systems of Central Asia, including the Tibetan Plateau in China and the Altai and Khangai mountain systems of Mongolia, comprise this ecological zone. The mountains of Japan also form part of the zone.

In the lower mountains of north-central China, mean annual temperature decreases from 14°C in the warmer eastern low hills to 8°C in the cooler western highlands. The difference in the July mean temperature is 20° versus 26°C between east and west, whereas January varies between 0° and -10°C. Similarly, mean annual precipitation typically averages 800 to 300 mm between east and west, most of which falls during summer. Nevertheless, this transitional region is seasonally moist enough to support monsoon vegetation.

On the Tibetan Plateau, temperature distribution generally follows elevation contour lines. Mean annual temperature goes from the 6° to 10°C range around 3 000 m, to 3° to 7°C above 4 000 m, to below -2°C above 5 000 m. Annual mean precipitation follows an east-west gradient from 800 mm on the eastern rim of the plateau to less than 50 mm in the west near the Pakistan-Afghanistan border.

The climate of the Mongolian mountain systems is characterized by widely ranging temperatures, both throughout the year and during the day. Annual precipitation ranges from approximately 200 to 600 mm, most of it falling during the second half of summer.

The transitional region of eastern China, including the Yellow Loess Plateau, has only limited natural forests, mostly in the high, inaccessible mountains. These forests are characterized by Pinus tabulaeformis, P. bungeana, Picea wilsonii, P. meyeri and Larix principis-rupprechtii, individually forming their own pure stands or sometimes mixed with a small amount of Abies nephrolepis. On the Yellow Loess Plateau and the surrounding areas, local residual woodlands are scattered with such similar species as Pinus tabulaeformis but also P. armandii, Platycladus orientalis, Sabina chinensis, Quercus liaotungensis, Q. baronii, Populus davidiana, Betula platyphylla, Fraxinus chinensis, Toxicodendron vernicifluum and Zelkova sinica as well as Acer and Tilia species.

Natural forests are better preserved in the western, higher mountains in the provinces of Gansu, Shanxi and Sichuan. Both conifer and broadleaf forests are present in these mountains. Abies faxoniana and Picea asperata dominate alpine conifer forests at 2 500 to 3 800 m. Conifer species that prefer a warmer environment, such as Picea wilsonii, P. brachytyla, P. complanata, Tsuga chinensis and T. dumosa, occupy lower elevations of 2 000 to 3 000 m or sometimes at 3 400 m, forming pure stands. Among the medium-elevation conifer forests are Pinus tabulaeformis and Cupressus chengii in pure stands. They grow from around 1 300-1 400 m to 2 100 m. Pinus armandii forests can extend up to 2 700 m. Deciduous broad-leaved forests are less prominent. Betula platyphylla, B. albo-sinensis, B. utilis and Populus davidiana are the most common species on the 2 600 to 3 500 m slopes, associated with Tilia chinensis, Acer spp., Dipteronia sinensis, Populus cathayana and P. purdomii in mixed forests.

There is a great diversity of mountain vegetation in Mongolia. The forest belt mainly contains larch forests, sometimes mixed with Siberian cedar or stone pine (Pinus sibirica) and spruce or fir. On sandy sediments on the lower slopes pine stands dominate and, together with larch, form the forest-steppe belt. In Mongolian-Altai the forest belt is often absent. The forest belt of the Khangai Mountains is in the range of 1 800 to 2 300 m with larch stands. Thickets of Salix spp. and Potentilla fruticosa, with occasional larch, cover the broad river valleys.

In Japan, the lower mountain zone is covered with deciduous beech forest dominated by Fagus crenata and Quercus crispula. The subalpine belt supports coniferous forests with Abies mariesii and/or A. veitchii. The altitudinal lower limit of the coniferous forests becomes gradually higher southwards, ranging from 700 m in northern Honshu to 1 500 m in central Honshu. Mixed forest of Thuya standishii and Tsuga diversifolia is present on ridges with shallow soils in the subalpine region of Honshu. Betula ermanii and Alnus maximowiczii are deciduous trees found in the subalpine and alpine regions. Mixed or pure stands are developed on boulders and shallow soils along snow valleys and on subalpine volcanic habitats. Prevailing coniferous forests on Hokkaido are dominated by Picea jezoensis and Abies sachalinensis, sometimes accompanied by Picea glehnii.

BOREAL CONIFEROUS FOREST

This zone is confined to the northern part of northeastern China. The zone is essentially Daxinganling (the Greater Xingan Range), a medium-altitude plateau. The zone has a rigorous climate with a long, cold winter. Mean annual temperature ranges between -1° and -6°C, the mean minimum of the coldest month is below -25°C and the extreme low is below -45°C. Soils are either permafrost or frozen for most of the year. Relatively warm summers bring a monthly mean temperature of 15°C in the warmest months with a growing season of about 90 days. Most of the annual mean precipitation of 500 mm falls during the summer season.

Forests in this zone are mostly simple, natural stands of three types. First, Larix gmelini is widely spread on 300 to 1 100 m slopes. It forms large, pure stands as well as mixed stands with Betula platyphylla, Populus davidiana and Quercus mongolica. Second, Pinus sylvestris var. mongolica forests are mostly distributed in the north between 300 to 900 m. They mostly form small pure stands. Third, Pinus pumila dominates on mountain tops or ridges of 1 100 to 1 400 m, forming low stands. In addition, Pinus sibirica forest is found in the northwestern portion of the Daxinganling. Among deciduous broad-leaved forests, Betula platyphylla and Populus davidiana grow as natural second-growth forests following disturbance of Larix gmelini, either in pure stands or in mixtures. Quercus mongolica forests are found in the south on dry, south-facing slopes below 600 m. Deciduous broad-leaved mixed forests, composed of Populus suaveolens, Chosenia arbutifolia, Ulmus davidiana var. japonica and Salix spp. are scattered along the Heilongjiang River and its tributaries.

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